-
Notifications
You must be signed in to change notification settings - Fork 272
/
MinimalIterator.swift
54 lines (45 loc) · 1.63 KB
/
MinimalIterator.swift
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
// Loosely adapted from https://github.com/apple/swift/tree/main/stdlib/private/StdlibCollectionUnittest
/// State shared by all iterators of a MinimalSequence instance.
internal class _MinimalIteratorSharedState<Element> {
internal init(_ data: [Element]) {
self.data = data
}
internal let data: [Element]
internal var i: Int = 0
internal var underestimatedCount: Int = 0
public func next() -> Element? {
if i == data.count {
return nil
}
defer { i += 1 }
return data[i]
}
}
/// An iterator that implements the IteratorProtocol contract in the most
/// narrow way possible.
public struct MinimalIterator<Element>: IteratorProtocol {
internal let _sharedState: _MinimalIteratorSharedState<Element>
public init<S: Sequence>(_ s: S) where S.Element == Element {
self._sharedState = _MinimalIteratorSharedState(Array(s))
}
public init(_ data: [Element]) {
self._sharedState = _MinimalIteratorSharedState(data)
}
internal init(_ _sharedState: _MinimalIteratorSharedState<Element>) {
self._sharedState = _sharedState
}
public func next() -> Element? {
_sharedState.next()
}
}